This application provides an apparatus and method for the reduction of blocking signals that occur in concurrent mode operation when a mobile station operates with two different air interfaces on different carriers within the same RF band. The increasing plurality of air interfaces worldwide creates the expectation that a mobile station would be able to operate concurrently with two or more air interfaces, referred to as concurrent multimode operation. Concurrent operation consists of a terminal operating with a voice or data call on one air interface (or mode of wireless communication), such as GSM, while scanning for access control signals (e.g., pilot channel signals, access channel signals, paging channel signals, and the like) from a second air interface in the same band, such as WCDMA, or vice versa. This allows a mobile station to optimize its performance over the available communications channel based on which air interface provided the optimum quality of service (QoS).
Concurrent multimode operation also allows the terminal to switch to a different standard in situations where low signal levels exist on one air interface (mode) but not another. Typically, the first and second air interfaces are supported by different base stations, but they could be supported in a single base station structure. The consequence of dual mode operation, however, is that the input to the receiver stage operating in a scanning mode for a second air interface may experience a strong blocking signal. For example, the transmit level for GSM ranges from +24 dBm to +30 dBm. For WCDMA terminals the maximum expected blocking level at the antenna input is −25 dBm. Because of the high blocking level, a conventional multi-mode mobile station is often unable to adequately scan or communicate in the second mode while the first mode is active.
Therefore, there is a need in the art for an improved apparatus and method for interference cancellation in wireless mobile stations operating concurrently on two or more air interfaces.